Parting agent for sprayed metal shells and method for making such shells



United States Patent Ofiice Meme,

l 2 3 077 647 giade up of the least expensive ingredients, all proportions eing set forth herein and in the claims as percent by PARTING AGENT FGR SP A METAL SEELLS weight. Such a mixture has been found suitable for form- AND METHOD FOR MAKING SUCH SHE Ls ing both a relatively complex contoured copper shell for Alfred E. Kugler, Warren, Mich, assignor to General Motors Corporation, Detroit, Mich a corporation of Delawar No Drawing. Filed July 13, 1959, Ser. No. 826,490 tamping die. In each case the sprayed metal was found 6 Claims, 1, 22 193) to be tightly adherent while the final metal shell was This invention relates to a parting agent for sprayed 10 It has been found that the desired results may be obmetal shells and to the method for making such shells and tained regardless of whether the pattern 18 formed of such more particularly to a COInPOSli'OI] adapted to be applied widely different materials as wood, clay, plaster of Paris, to a pattern or form for use in making sprayed metal or metal e range of compositions found to be best shells and to the method for making such snells whereby suited for the treatment or conditioning of the pattern tight adherence between the pattern and the sprayed metal surface is as follows: shell is assured while at the same time enabling their P nt ready separation. Polyvinyl alcohol 18-55 While it has been known that the metal spray technique Silica flour 20-60 may be used to build up a metal shell upon a pattern Ethyl alcohol 15-30 formed of such materials as Wood or plaster of IZaris, such 20 Another cumposltlon found to be Well Suited to forming ally unsatisfactory as electrode materials where the sprayed metal shell is to be used as an electrode in such operations as electrical discharge machining. Similarly, these The molten .metal 15 sprayed under i pressure poor wear resistant qualities.

Accordingly, it is an object of my invention to provide a composition suitable for coating a pattern or form to the final She I have l 3 332;? gigggg gfgaj melting p 01m meta S m spraying after cleaning, the surface of the pattern with Having described my invention in terms of its preferred shell While enabling their ready separation.

In order to maintain fidelity of reproduction of the contour of the pattern over a wide range of complexity, I have found it to be essential that the sprayed metal adpletion, the sprayed metal shell must be easily parted from the pattern without damage. Obviously, these two generally conflicting requirements must be reconciled to enable successful metal spraying. As a result of extensive investigation I have found that both low temperature metals such as zinc and tin and high temperature metals such as copper, steel, nickel 4 r D am vnomium l'ncludmg than anoya may be ggi g duplicated, depositing on the coated surface sprayed metal moval from the pattern. More specifically, I have found that a liquid mixture comprising polyvinyl alcohol, a fine grain powder such as silica flour, powdered graphite or powdered copper, and sufficient thinner, such materials, i.e., methylethyl ketone and ethyl alcohol being well ing essentially of a mixture of about 18 to 55% polyvinyl alcohol, about 20 to 60% silica flour and about 1530% thinner, said silica fiour having a maximum coarseness of about 200 mesh size.

2. In a method of making a sprayed metal shell, the

moval of the sprayed metal shell. I have also found that 4 I i n a in th d f the powder material should have a maximum coarseness of steps of lili g tge jge i ii s e l fc iifh in cl ini about 200 mesh Size While having 110 Practical limit 011 to the surface of the pattern the contour of which is to be the degree of fine e duplicated, depositing on the coated surface sprayed metal I Preffir to use a mixture conslstlng of about 59% p yto the desired thickness, and removing the resulting metal vinyl alcohol about 25% silica flour (200 mesh size) and shell from the pattern without dama about 25% by weight etnyl alcohol such a mixture being 5 A parting composition for coating the surface of a highly eifective for the purpose intended while being pattern to be metal sprayed for building up a shell tightly adherent to and easily removed from the pattern consisting essentially of a mixture of about 36% polyvinyl alcohol, about 43% silica flour, and about 21% ethyl alcohol, said silica flour having a maximu mcoarseness of about 200. mesh size. 5 6. In a method of making a sprayed metal shell, the

steps of applying the parting agent set forth in claim 5 to 2,639,213 the surface of the pattern, the contour of which is to be 2,744,011 duplicated, depositing on the coated surface sprayed metal ,5 9

to the. desired thlckneess, and removing the resulting metal 10 2,892,227 shell from the pattern without damage.

References Cited in the file of this patent UNITED STATES PATENTS Cozza June 30, 1947 Hugger Mar. 3, 1953 Barth May 19, 1953 Samuel et a1. May 1, 1956 Halpern n Mar. 24, 1959 Operhall June 30, 1959 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N00 3,077,647 February 19, 1963 Alfred E, Kugler It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 62, for "25% alcohol" read 25% ethyl alcohol column 3 line 4, for "maximu mcoarseness" read maxlmum coarseness line l0 for "thickneess" read thickness column 4, line 4., for "2,42l 373 Cozza June 30 1947" read 2,421,373 Cozza June 3, 1947 Signed and sealed this 10th day of September 1963,

(SEAL) Attest:

DAVID L. LADD Commissioner of Patents ERNEST W. SWIDER Attesting Officer 

1. A PARTING COMPOSTION FOR COATING THE SURFACE OF A PATTERN TO BE METAL SPRAYED FOR BUILDING UP A SHELL TIGHTLY ADHERENT TO AND EASIALY REMOVED FROM THE PATTERN CONSISTING ESSENTIAALLY OF A MIXTURE OF ABOUT 18 TO 55% POLYVINYL ALCOHOL, ABOUT 20 TO 60% SILICA FLOUR AND ABOUT 15-30% THINNER, SAID SILICA FLOUR HAVING A MAXIMUM COARSENESS OF ABOUT 200 MESH SISH SIZE. 